With the rapid progress of display technology, semiconductor element technology, as the core of display devices, has also made a leap in advancement. For known display devices, Organic Light Emitting Diode (OLED for short) are being used more and more in high-performance display areas as a current-type light emitting device because of having characteristics such as self-luminescence, fast responding, wide viewing angle, and capability of being fabricated on flexible substrates. OLED may be divided into two types of Passive Matrix Driving OLED (PMOLED for short) and Active Matrix Driving OLED (AMOLED for short), AMOLED display is expected to replace liquid crystal display (LCD for short) to be a next-generation new flat panel display, for it has advantages such as low manufacturing cost, high response speed, power saving, capability of being applied to DC driving of portable devices, a wide range of working temperature etc.
However, in technical solutions of the prior art, as for a large-sized AMOLED display, a plurality of thin film transistors (TFTs for short) are disposed on an array substrate of the AMOLED display. In order to increase carrier mobility of said TFTs and reduce resistivity, and thereby lessen power consumption when the same current flows through, usually polysilicon is adopted to constitute said TFTs. However, due to manufacturing process and characteristics of polysilicon, when a TFT switching circuit is fabricated on a glass substrate of a large area, often there are fluctuations of electrical parameters such as threshold voltage Vth, mobility and so on, so that the current flowing through the OLED device not only changes with a change of on-voltage stress caused by long-term turning-on of the TFTs, but also varies depending on drifting of the threshold voltage Vth of the TFTs. In this way, luminance uniformity and luminance constancy of the display will be affected.
In summary, in displaying process of the AMOLED display, luminance uniformity may be decreased due to drifting of the threshold voltage, which may cause an image quality of the display to be lowered.